Bottom Line:
We used a public goods game with third-party punishment to test whether punishment of defectors was reduced when defecting was typical, as predicted if punishment is responsive to norm violation.The cost of punishment was fixed, regardless of the number of players punished, meaning that it was not more costly to punish typical, relative to atypical, behaviour.We suggest that the reduced punishment of defectors when they are common might often be explained in terms of the costs to the punisher, rather than responses to norm violators.

ABSTRACTPunishment of defectors and cooperators is prevalent when their behaviour deviates from the social norm. Why atypical behaviour is more likely to be punished than typical behaviour remains unclear. One possible proximate explanation is that individuals simply dislike norm violators. However, an alternative possibility exists: individuals may be more likely to punish atypical behaviour, because the cost of punishment generally increases with the number of individuals that are punished. We used a public goods game with third-party punishment to test whether punishment of defectors was reduced when defecting was typical, as predicted if punishment is responsive to norm violation. The cost of punishment was fixed, regardless of the number of players punished, meaning that it was not more costly to punish typical, relative to atypical, behaviour. Under these conditions, atypical behaviour was not punished more often than typical behaviour. In fact, most punishment was targeted at defectors, irrespective of whether defecting was typical or atypical. We suggest that the reduced punishment of defectors when they are common might often be explained in terms of the costs to the punisher, rather than responses to norm violators.

RSBL20140388F1: The proportion of PGG players who were punished by player 5, according to their PGG decision and whether this violated the descriptive norm. Sample sizes for each condition are indicated in parentheses. Error bars show standard errors.

Mentions:
In general, typical and atypical behaviours were equally likely to be punished (proportion of typical behaviour punished = 0.17 ± 0.02; versus atypical = 0.22 ± 0.04; table 1). In addition, defectors were just as likely to be punished whether their behaviour was typical (0.36 ± 0.03) or atypical (0.36 ± 0.05; table 1 and figure 1). Similarly, cooperators were rarely punished, regardless of whether their behaviour was typical (0.02 ± 0.01) or atypical (0.01 ± 0.01; table 1 and figure 1). Cooperators were never singled out for costly punishment and only faced punishment when all members of their group were also punished (on three occasions). Furthermore, when player 5 invested to punish defectors, they always punished all defectors in the group rather than singling one individual out for punishment. Punishment was linked to gender, with male players being more likely to punish than females (proportion of individuals that were punished by males = 0.22 ± 0.02; versus females = 0.12 ± 0.02; table 1).Table 1.

RSBL20140388F1: The proportion of PGG players who were punished by player 5, according to their PGG decision and whether this violated the descriptive norm. Sample sizes for each condition are indicated in parentheses. Error bars show standard errors.

Mentions:
In general, typical and atypical behaviours were equally likely to be punished (proportion of typical behaviour punished = 0.17 ± 0.02; versus atypical = 0.22 ± 0.04; table 1). In addition, defectors were just as likely to be punished whether their behaviour was typical (0.36 ± 0.03) or atypical (0.36 ± 0.05; table 1 and figure 1). Similarly, cooperators were rarely punished, regardless of whether their behaviour was typical (0.02 ± 0.01) or atypical (0.01 ± 0.01; table 1 and figure 1). Cooperators were never singled out for costly punishment and only faced punishment when all members of their group were also punished (on three occasions). Furthermore, when player 5 invested to punish defectors, they always punished all defectors in the group rather than singling one individual out for punishment. Punishment was linked to gender, with male players being more likely to punish than females (proportion of individuals that were punished by males = 0.22 ± 0.02; versus females = 0.12 ± 0.02; table 1).Table 1.

Bottom Line:
We used a public goods game with third-party punishment to test whether punishment of defectors was reduced when defecting was typical, as predicted if punishment is responsive to norm violation.The cost of punishment was fixed, regardless of the number of players punished, meaning that it was not more costly to punish typical, relative to atypical, behaviour.We suggest that the reduced punishment of defectors when they are common might often be explained in terms of the costs to the punisher, rather than responses to norm violators.

ABSTRACTPunishment of defectors and cooperators is prevalent when their behaviour deviates from the social norm. Why atypical behaviour is more likely to be punished than typical behaviour remains unclear. One possible proximate explanation is that individuals simply dislike norm violators. However, an alternative possibility exists: individuals may be more likely to punish atypical behaviour, because the cost of punishment generally increases with the number of individuals that are punished. We used a public goods game with third-party punishment to test whether punishment of defectors was reduced when defecting was typical, as predicted if punishment is responsive to norm violation. The cost of punishment was fixed, regardless of the number of players punished, meaning that it was not more costly to punish typical, relative to atypical, behaviour. Under these conditions, atypical behaviour was not punished more often than typical behaviour. In fact, most punishment was targeted at defectors, irrespective of whether defecting was typical or atypical. We suggest that the reduced punishment of defectors when they are common might often be explained in terms of the costs to the punisher, rather than responses to norm violators.